This invention relates to a mixing apparatus for producing multi-component materials, in particular for producing foams based on polyurethane, consisting of storage containers for the components connected to conduits which are equipped with feed pumps and open into a mixing chamber through nozzles or injection openings, a receiving chamber being arranged in line with the outlet aperture of the mixing chamber.
These mixing apparatus are used for filling molding tools with the reaction mixture. Since the mixing apparatus must operate with interruptions due to the filling operations, difficulties arise particularly at the beginning of the mixing process because the components do not mix completely the moment they enter the apparatus. Some portions of the components might, therefore, enter the mold cavity unmixed and cause faults in the finished molded part.
This disadvantage was corrected by providing a receiving chamber opposite the outlet aperture or at a deflecting point of the sprue channel. This receiving chamber was used to catch the first portion of the imperfectly mixed reaction mixture, which was vigorously stirred by the following stream of mixture and then replaced by new mixture because the quantities continuously discharged from the receiving chamber were also introduced into the mold cavity.
This receiving chamber has, however, the disadvantage that the residue of mixture left in it must either be removed by blowing it out before it has completely reacted or the molding tool must be so formed that the contents of the receiving chamber can be released together with the contents of the mold cavity. In either case, the residue of mixture in the receiving chamber is wasted. Furthermore, it has not to date been possible to produce moldings which are free from a sprue seam when a receiving chamber is used.
One object of this invention is to provide a mixing apparatus in which loss of material is prevented in spite of the presence of a receiving chamber. It should preferably be possible to produce moldings without sprue seams.